Earphones have become common electronic equipments in people's daily life; in particular, anti-interference earphones that can reduce noise are more and more favorable for users. As noise is shielded, users can easily use anti-interference earphones to listen to music or use a telephone in a noisy environment such as subway trains, shopping malls, and roads and so on. On the other hand, however, because the anti-interference earphone shield most of the sound in an external environment, the user may not be able to hear an abnormal sound in the external environment and may not be aware of possible danger and may be harmed.